The present invention disclosed herein relates to a method of analyzing the prognosis of cervical cancer according to human papillomavirus (HPV) DNA integration pattern, and more particularly, to a method of observing the pattern of the DNA of high risk-human papillomavirus (HR HPV), which is present in cervical cancer tissues, being inserted into human cervical cancer cells by in situ hybridization (ISH), and then analyzing the prognosis of a patient after radiotherapy according to the integrated pattern of the HPV DNA.
Human papillomavirus (HPV) in high risk group induces invasive cervical cancer while causing a persistent infection in human cervical cancer tissues over a span of a few years to a few tens of years. According to the Korean cancer registration statistics data in data, although the frequency of invasive cervical cancer is reduced from 19.3 to 10, frequency of cervical intraepithelial neoplasia, which is considered as a previous stage of invasive cervical cancer, is increased to 19 per hundred thousand people in 2010 from 7.5 per hundred thousand people in 1993. This implies that the gynecological cancer associated with the infection of the human papillomavirus in high risk group still remains as an important issue with respect to the incidence of gynecological cancer. According to the recent Korean cancer registration statistics, there are about 3700 to 3800 new cancer patients each year, and they are being treated using surgical operations, radiations, anticancer agents, etc., either alone or in combination. For cancers in clinical stage 1, surgical operations are performed mostly. However, when the tumor size is big or there is a lymph node metastasis, or for cancers in clinical stage 2, radiotherapy becomes the major therapy. In Korea, the five-year survival rate in cervical cancer patients is about 80%, being relatively higher than those of other countries. However, the death rate due to cervical cancer is still ranked third worldwide.
In general, human papillomavirus-related cancer species are sensitive to radiations and thus can be treated well by radiotherapy but the adverse effects of radiotherapy have a room for improvement. Additionally, since this disease is well treated by radiotherapy, the reduction in the levels of radiation and anticancer agents, which were typically used in the past to a particular group of patients, may improve the quality of patients' lives while capable of increasing the rate of complete cure.
Instead of the current uniform therapies, the development of a therapeutic method which includes classifying the patients into a low risk group and a high risk group, and applying a lesser amount of radiation and a minimal amount of anticancer agents for patients in the low risk group, whereas applying a treatment for improving the complete cure rate for patients in the high risk group, will enable the increase of complete cure rate of cervical cancer worldwide and the improvement in the quality of cervical cancer patients' lives than what they enjoy at present.
In the typical technologies, US Patent Application Publication No. 2004-0248107 discloses probe sets for the detection of high grade dysplasia and carcinoma in cervical cells, and a method for detecting HPV infected cells using ISH method, and Gernot Hudelist et al. disclose a method for observing the physical patterns of HPV DNA (episomal, mixed and integrated form) according to the stages of cervical cancer (CIS, CIN1, CIN2, and CIN3) by polymerase chain reaction (PCR) (Gynecologic Oncology, 92: 873, 2004). However, these typical methods of analysis involve detecting the tissues where the high risk HPV is present, and then examining the presence of pre-invasive cancer (cervical intraepithelial neoplasm (CIN I, CIN II)), where HPV has been analyzed to be infected or integrated only in an episomal form; and in situ cancer (CIN III) and invasive cancer, where HPV has been analyzed to be present in an integrated form, and thus simply provide a method of distinction whether it will be progressed into a cancer or it is a pre-cancerous lesion, and these methods had a limitation in that it cannot provide a clear distinction from stage IV to stage IVB of locally advanced cervical cancer.
Meanwhile, in the previous studies, the present inventors had classified the cervical cancer patients into four groups according to the results of real-time qPCR performed using probes and primers specific to E2 hinge region and E6 ORF, and had reported that the integrated HPV DNA pattern was associated with the results of therapeutic treatment of cervical cancer patients by radiation (Shin, H. J. et al., PLoS One, 9:e78995, 2014).
However, the determination of the HPV DNA integration pattern and presence of HPV infection by PCR alone lacks in accuracy of distinction between the tumor tissues having an episomal form and those having multicopy tandem-repetition integrated HPV. Additionally, there is a limitation in that when the episomal form and other integration patterns are co-present in the same tissue, it is difficult to figure out the presence ratio of each form and observe the integration form of HPV DNA according to the location within the tumor tissue.
Under these circumstances, the present inventors have made intensive efforts to develop a method for an accurate and convenient analysis of the prognosis of invasive cervical cancer through observation of the HPV DNA integration pattern within the cervical cancer, and as a result, they have discovered that the prognosis of patients after radiotherapy can be effectively analyzed according to the DNA integration pattern, by observing the pattern of HPV DNA integrated in the cervical cancer cells using in situ hybridization (ISH) method, and also confirmed that when the HPV DNA integration patterns were classified by the above method, the prognosis of cervical cancer patients having the episomal pattern and the integrated pattern was clearly distinguishable, thereby completing the present invention.